Train control



April 23,- 1929. c. s. BUSHNELL TRAIN CONTROL Filed Get. 21 1922 VENTOR BY M TiORNEY Patented Apr. 23, 1929.

UNITED STATES PATENT OFFICE.

CHARLES S. BUSHNELL, OF ROCHESTER, NEW YORK, ASSIGNOR TO GENERAL RAIL- WAY SIGNAL COMPANY, OF GATES, NEW YORK, A CORPORATION OF NEW YORK.

TRAIN CONTROL.

Application filed October 21, 1922. Serial No. 596,102.

This invention relates to automatic brake applying mechanisms adaptable for automatic train control systems.

In automatic train control. systems, it hc comes necessary to act upon the regular airbrake system now in common use and produce an automatic application of the brakes, preferably a service application, under certain conditions of trattic, speed of train, or the like. The particular conditions of traffic or speed under which the automatic brake application should occur, are not material to the present invention which deals particularly wit-h the means for giving such an application cliectively, efficiently, and in such a manner as not to endanger the train itselt.

lVith the ordinary automatic air-brake system in common use upon railroads, a serw ice brake application is given by venting the brake pipe at a limited rate. After the normal running brake pipe pressure has been reduced to a certain value, turther reduction does not add to the braking effect, because the auxiliary reservoir pressure and brake cylinder pressure are equalized. Consequently in making an automatic brake application, it is desirable to limit the amount of reduction in brake pipe pressure to an amount not to exceed that necessary for eqliialization, otherwise there is a useless waste of air which must be replaced before the brakes can be released.

The automatic brake application under consideration, should preferably be one which the engineer can not oppose or prevent. \Vith the ordinary air-brake system, however, with the engineers brake valve in releas .d position or even the running position, the brake pipe may be kept up to pressure in spite of the venting thereof by the automatic mechanism. Hence, it is important in making the automatic brake application. to also disconnect the engiueefls brake valve from the main reservoir, so that the brake pipe pressure can positively be reduced irrespective of the position of the engiiu-ers brake valve.

Forvarious reasons, it considered preferable, particularly for freight trains, to make the amount of reduction in brake pipe pressure dependent upon the speed of the train at the time the reduction made. For one thing, a heavier brake application can be safely made on a freight train at higher speeds than at lower speeds.

Generally stated, the primary objects and purposes of this invention are to provide a simple and reliable brake applying mechanism which will make a predetermined reduct-ion in brake pipe pressure from the normal running brake pipe pressure, and automatically cut off the connection from the main reservoir to the engineers brake valve, and will make a reduction in brake pipe pressure to different degrees depending upon the speed of the train at which the automatic brake application occurs.

Other specific objects, characteristic features, and advantages of the invention will appear hereinafter as the description progrosses. In the accompanying drawings,

Fig. 1 shows in a simplitied and diagrammatic manner the parts and circuits embodying this invention, these parts being shown more with the view of making it easy to understand the invention than with the idea of showing the precise construction prefiiirably employedin practice; and

Fig. 2 is a diagrammatic plan view of the rotary valve of the usual engineers brake valve, showing the additional port and cavity added thereto for the purposes of this invention.

It is assumed that the brake applying mechanism shown in Fig. 1 will be controlled electrically in some suitable manner, dependent upon receiving a stopping influence from the trackway, the existing speed of the train, or other conditions. all of which forms no part of this invention. The primary control tor the brake applying mechanism is exerted by an electro-pnenmatic-valve EPV, the coil or winding 1 of which is connected to a suitable device and source of current which scrvesto deenergize this winding at the time and under the conditions it is desired to produce an automatic brake application with the main reservoir by a pipe 6.

Piston 5 has a small leakage hole 7 therein establishing comn'iunication between the valve chamber 3 and the cylindrical chamber 8 in which the piston 5 moves. A spring 9, strong enough to overcome the frictional opposition to the movement of piston 5 and the slide valve 4: tends to move said slide valve to the left as shown. The cylindrical portion 8 of the mlve chamber is connected by pipe 16 to the small chamber 10 in the bottom of the electro-pneumaticvalve EPV. This chamber 10 is connected to atmospl'iere through a vent port ll. when the electro pncuniatic-valve EIV deenergized. The slide *alve 4. controls the connection bet-ween arious ports and passages in the valve A, but these passages are more conveniently described in connection with the operation.

In the lower part of the appli ration valve A. o as a separate device if desired, is an equalizing: piston 12 and valve 13, correspomlinc in structure and function to the equalizing pison and valve jtoi'iniijig part of the 1., i'ualv engineers brake alive.

In determining the amount of reduction in brake pipe pressure to be made, it is preferred to compare volumes by allowing a. predetermined volume of air at the norina l brake pipe pressure to 'ape from a special equalizing rese 'V)ll into a reduction chamber at atmospheric pressure. These reservoir-:2; having a ratio of volumes orresponding to the amount or reduction desired, automatic venting of the brake pipe is arrested when the pressure therein has been reduced to that equal. to the resultant pressure in the equalization chamljier or reservoir and the reduction chalnb or chambers. In Fig. 1, the equalizing chamber or reservoir 's normally charged at brake pipe pressure, and is designated E. The reduction reservoir or chamber, is, in the particular embed linen t shown... divided into three parts ll, ll and R The reduction cluimber R connected to the application valve it directly by pn es ll and 15. The reduction chamber R is connected to the application valve when an OlCCtITO})11UillihttlCfiltlil M is decnergized; and similarly the reduction ehambe' IF connected to the application valve when an clcctro pneumatic-valve II is deeuergizied.

In the uiinpliticd construction shown, the electro-pncumatic-valres It and M each cone pri c an electro-maegnet oi" ".ic iron-clad type having a coil and an armature and core The core L1 is connected to a diaphragm preferably of metal forming the upper part of a valve casing .23. This diaphragmi is urged upward by a spring 2i and has lixed thereto a pin *a-lve adapted to control the flow of compressed air from the pipe 52C, or the pipe 17, connected by pipe 15 to the application valve, to the expansion resem'oirs B and R Another element of the brake applying: mechanism constitnting this invention. is a. pneumatte-ally operated pin valve V. This valve V comprises upper and lower rbaun hers QT and 28 scpa 'ated b a flexible diaphragm 29. The upper cl amber is in connnunication by pipe 30 to the pipe run- 11in in. the usual locomotive air-brake equipment from the engineer-e1 brake lve to the emcss-prcssure governor top ot the pump governor. The lower chamber :29 is connected by pipe 31. to the bralze pipe. Con nected to the diaphragm F3! is a valve 1; raised by a. sprint: il l to its closed position, muting o'll communiation 'tl't lll the lower chamber 25% to pip: ill leading; to the applisatiou valve A. I

iinother clement oil? the system is l b suitable speed-responsive device or governor (l, which is coupled to the wheels or axles or is driven in some other suitable my in ar i'ordance with the actual speed of the locomotive or other vehicle. This spced-responiire device G is shown in a simplified torn: in. the drawings and acts in a wcll-known manner raise an insulated collar or disk to dititerent positions dependent upon the :u-tnal speed; the higher the spent, the higher the position of the collar 35. Located in the path of movemei t of the collar 235 are two pairs of contact springs or lingers 3 .3 and 3? which are arranged as shown so as to he opened wh n the s ;)eedresponsive device indicates the diiffercnt speed limits. The speeds at which the respective pairs of contacts Ill; and $37 open may be varied of course in p 'actice to suit particular working conditions. For ordinary freight service, a typical (organization is one in which both of the contacts 1-36 and 37 are closed below 20 miles per hour. the co itacts 37 opening above 20 miles per hour. and, contacts 36 opening above 2." miles per hour.

Qwermv'on. The varii'ius in Fig. 1 in the normal prstiiou, that is. the position while the train is running without a brake application and under conditiims ct: speed or otherwise where it unnecessary to produce an automatic brake application. The eleetropneumatic-valve El 7 is energized and closed, preventing the escape of air to atmosphere lroin the right hand side o l the piston 5. Main reservoir 'iressure, thrrelore, builds up through the leakage port T to the same pressure on opposite sides oi the 1 lnloii 5, which is then moved by spring; 9 to the lett hand position, shown. The engineeifis brake alve will be in the running posi ion. normal conditions bein assun'ied and with the bra lit alve in this running; position, main rcscrvoi r p endure supplied through ports in the en gineers valve to the pipe cadingg' to the excess-presetre ,e overnor head, thereby supplying pressure through pipe 30 to upper chamber 27 againstdiaphragm 29 and opening parts are shown Ill) valve 32. The high and medium speed valves H and M are deencrgized and their respective valves 25 opened as shown. The pressure conditions, with the parts in the normal position, are as follower-Main reservoir pressure is supplied from valve chamber 3 to port 38 to the engineers brake valve, permitting the engineer to recharge and release in the usual way. Brake pipe pressure exists on the lower side of equalizing piston 12 by reason of pipe connection 39. Brake pipe pressure also is supplied through pipe 31, valve 32which is opened, pipe 34:, port 40, cavity ll in slide valve it, port 42 to the upper side of the equal izing piston 12. The port or passage 42 has an o pcni o g through passage a3, pipe 4A, to the equalizing reservoir E, so that said reservoir is charged a t the existing brake pipe pressure. The expansion reservoirs It, It and R are all connected to atn'iosphere through pipe 15, lassage -15, avity 46 in slide valve =1 and port at? to atmosphere. The passage 48 from the underside of the equalizing piston valve 13 is blanked at cavity 19 of the slide valve 4.

Assun'ie the parts in the normal condition described, and that on account of excess speed or otherwise, an automatic brake implication necessary. Further, assume that the engineer has not made any manual amilication. Upon decnergization of the clcctro-piicumatic alve EPV and the opening thereof, pressure on the righthand side of piston 5 is vented to atmosphere through exhaust port 11; and since this exhaust port 11 is much larger than the leakage port 7, pressure on the righthand side of piston 5 drops quickly, so that main reservoir pressure on the lefthand side oil said piston forces it, together with its slide valve t, over to the extreme righthand position in opposition to spring 9. This movement of the slide valve 4: blanks port 38, cutting' oli' communication from the main reservoir to the engineer's brake valve, so that whether the enginccrs brake valve is in the running, holding, orfrclease positions, there is no tend to the brake pipe. This is necessary, as hereinl'ietore explained, in order 'to insure prompt and cllicicnt venting of the brake pipe pressure to product an effective brake application. ith the slide valve l: shifted the equalizing reservoir E is connected to pipe l5 leading to the rtuluction reservoirs by cavity 46. the port ill leading to the brake pipe being: blanked. The passage 4.8, leading to the equalizing piston valve is connected by cav itv t?) to port 47, leading to atmosphere. Thus, existing brake pipe pre ore is tIaIlflJtd, so to speak, in the equalizing reservoir E, this reservoir thrown in communication with the expansion reservoir R, and the resultant no is applied to the upper face of the qmlizing piston 12.

Assume that the speed is below, say miles per hour, at the time of the automatic operation above described, so that contacts 86 and 37 are both closed. Upon deenergization of the electro-pneumatic-valve EPV, therefore, closure of its contacts 2 establishes an energizing circuit which can be readily traced on the drawing for the valves 11 and M, which being energized, close their respective valves 25,so that the expansion reservoir R alone is connected to pipe 15. It will be evident that the volume of the equalizing reservoir E with respect to the volume of the reduction reservoir R determines the resultant or equalization pressure oiythese reservoirs, and likewise the pressure on the upper face of the equalizing piston 12. As a typical illustration, assume that these volumes are so proportioi'ied that their equalization pressure is 8 pounds lower than the former or initial pressure in the equalizing reservoir corrcspoluliup, to the former or initial brake pipe pressure. The equalizing piston 12 raises and opens its valve 13 to vent the brake pipe through the pipe 39, valve-l3 opened, passage 48, cavity 49, port 47 to atmosphere. This venting operation is similar to that which is produced by the equalizing" piston ot' the usual engineers brake valve. 'lren the pressure in the brake pipe has beenvented down to the point where it equals the equalization pressure of the reservoirs E and ll, valve 13 closes and stops further venting; and if the reservoirs E and It are proportioned, as above stated, so that their equalization pressure is 8 pounds lower than the initial pressure in reservoir E, a brake pipe reduction of 8 pounds has been made :uitomatically.

Assume next that the speed at the time of the automatic brake application is more than 20 miles per hour and less than 27 miles per hour, so that contacts 37 are opened while contacts 36 are closed. Magnet valve M is then tlQQ'flCl'g'iZPd, while magnet valve H is energized. The expansion reservoir R, as well as the reservoir it, is now connected to the equalizing reservoir E and the combined volumes of reservoirs It and R are proportioned to give the desired greater reduction for this speed, say 14 pounds. Similarly, it the speed at the time of the automatic application is more than 27 miles per hour, so

that contacts 36 are opened as well as contact 37, all three expansion reservoirs R, R and R are thrown into cou'ununication with the equalizing reservoir E, so that the equalization pressure is still lower and gives a still greater h 'ake pipe "reduction, say 20 pounds, or full equalization. The pressure in the equalizing reservoir E at once drops and equalizes with that in reservoir R, or R plus R or R, R and R together, as the case may be, so that subsequent reduction in speed, due to the automatic brake application, and the reclosing of contacts 36 or 37, energization of the valve magnets H or M, and closure of their valves 25, does not change the equalization pressure in the equalizing reservoir E. In other words, the amount of brake pipe reduction depends upon the instantaneous OXlStlllf speed at the time the brake application is initiated and is not changed by any subsequent reduction in speed.

As soon as the speed has been properly reduced by the auton'latie brake application, or :tor other reasons it is considered appropriate to discontinue the automatic applicatien, the eleetropnelunatic-valve EPV is reenergized by apparatus (not shown) which intended to be used to control. this valve,

as llereinbetore explained. This cuts oil fur-.

ther escape of air to atmosphere from the right hand side of piston 5, and main reservoir pressure quickly builds up on both sides ot said piston allowing it to be returned to the normal position shown by spring, 9. The return of the slide valve 4. to normal opens the port- 38, thereby reestablishing connection from the main reservoir to the engineers brake valve and permitting the engineer to release the brakes. Cavity 46 connects the IGtlUCl'iOTl reservoirs It, R and R to atmosphere. The cavity 41 connects the equalizing, reservoir E to the brake pipe so that pressure in said reservoir at once builds up as the brake pipe is recharged and normal conditions resumed.

From the toregoin it will be observed that the automatic brake applying mechanism of this invention serves to make a predetermined limited. reduction in brake pipe pressure, this reduction turther varying depend out upon the speed existing; when the brake application "is initiated. It the speed is high, a large reduction and a heavy brake application are made. If the speed is mediiinn, a lower reduction and a lighter brake application are made. it the speed low, a still lighter brake application. is made. This feature is C(llifilltltietl to he of pmrticular importance in connection with the brakin of freight trains, in which, on account 01 the length of train and delay in the 2 pplication and release of brakes on the several cars, the speed at which the brake application is made is an important factor in (letermining how heavy an application should be made. At liiws mals, say under 12 miles per hour, an automatic application of the brakes on a ion a freight train is liable to produce serious damage; and it may be explained here that it is contemplated in accordance with this invention that the control of the electro-pneumatic-valre EPV is such that, at lower speeds, under 12 miles per hour, for example, this e1ectro-pnclimatic-valve EPV is never deenergized. Above the low critical speed given 12 miles per hour, itis considered desirable to make the brake application dependent upon the speed, the higher the speed, the higher the permissible brake application.

While, according to specific embodiments shown, three degrees of brake application a re disclosed, it will be obvious that the same principle may be extended by the same or equivalent means to provide any desired number of different degrees of brake application depending on speed.

Assume now that, for some reason, the brakes are partially or fully applied manually at the time the electro-pncumatic-mlve IIQPV is deenergized to cause an automatic brake application. Obviously, it the brakes are already fully applied, it is unneces ary to iimrther reduce the brake pipe pressure, since any reduction in brake pipe pressure after full cqualimitiou of the auxiliary reservoir and brake cylinder pressure does not add to the braking e'li'ort and is a ttemled by the waste of air and other diszulvantages. However, it the brakes are only partially applied and the speed of the train is such to warrant a heavier appli .ation, and such heavier application is demanded in the interests of safety, a further reduction in brake pipe pressure should be made. This desirable result is accomplished by this invention. (:i'enerally stated, at eachv automat': a pplication, the normal running, brake pipe pressure is automatically reduced, with due regard to any reduction that may have already been made, to a predetermined extent depending upon the existing speed. This is accomplished by the operation of the valve V which. serves to trap, in the equalizing reservoir E, the normal running brake pipe pressure as soon as a manual reduction in brake pipe pressure initiated, so that irrespective of the amount of brake pipe reduction made manually, there always remains in the equalizing reservoir E, as a standard of measurement, the normal ri'lnning brake pipe pressure. As previously stated, the pipe 30 leading; to the upper chamber 27 above the diaphragm 529 is connected to the pipe of the usual locomotive air-brake equipment which runs from the engiueefs brake valve to the excess goveri'ior head. The function of this pipe and the pressures therein in the ordinary airbrake equipment are well-known. It the engineefis valve is in the release, running, or holding position, the pipe 30 is connected. to main reservoir pressure. 11, however, the eneineefis valve is in the lap, service, or en'iergency positions, the pipe 30 is disconnected .trom main reservoir pressure. These pressure conditions exist in the ordinary equipment and correspond to those employed to control. the so-called excess-pres sure governor top or head. Under certain conditions, for example, if the pump is running, pressure may be trapped. or left in the pipe 30 upon movement of the cnginecfis valve to a brake applying position; and to assure that the pipe 30 will always be exhausted Whenever the engineers valve is till shifted from its feeding positions, an additional cavity and port are preferably added to the rotary valve of the engineers brake valve, as shown in Fig. 2. This additional cavity 50 is connected by port 51 to the cen tral exhaust-passage of the engineers brake valve; and this cavity 50 is arranged to corn nect the port in the valve seat and leading to the excess-pressure governor head to atmosphere While the engineers valve is in the lap, service and emergency positions. It may be stated here that this particular arrangement as shown and described, including the connection of pipe 30 to the pipe of the ordinary equipment leading to the excessiiiressure governor head, has been adopted in order to take advantage as much as possible of existing equipmmit; and it will be apparent that other arrangements, such as a separate valve connected to the engineers brake valve or additional ports in the engineers valve may be employed to produce the desired operation of the valve V, that is, provide for pressure while the engineers valve is in the release, running or holding positions and absence of pressure while in the lap, service or emergency positions.

Assume now that the engineer makes a manual application of the brakes prior to the operation of the mechanism to produce an automatic b 'ake application. As soon as the engineer shil'ted his bra-kc valve to the service or cn'iergency position to make such manual brake application, pressure was cut oil' and exhausted from pipe 30, allowing spring 33 to close valve 32 and trap air at the for mer or normal running brake pipe pressure in the equalizing reservoir E. \Vhen, therefore, the electro-pneumatic-va1ve EPV is deeuergized and the application valve A operates in the manner described, the standard pro. are to which brake pipe will be automatically reduced is the same as it the engineer had made no previous manual application. In other Words, the pressure upon the upper side of the equalizing piston valve 12 do mds upon the equalization of pressure in reservoir E, combined with R, R and R as the case may be. Assuming that the speed is low, so that the resultant pressure in reservoir E is only 8 pounds lower than the normal running brake pipe pressure, it can be readily seen that, if the engineer has already made an 8 pound reduction in brake pipe N pressure, the equalizing piston 12 does not shitt, pressure on its underside being as low as or lower than that on the upper side. Consequently, if the engineer has made as great a reductionin brake pipe pressure as called for by the operation of the automatic mechanism, no further venting otthe brake pipe occurs. Suppose, however, that the speed 1s high and that a 20 pound reduction is do manded by the automatic mechanism, and suppose that the engineer has made only, say,

a 10 pound reduction manually. Then, the equalizing piston 12 is shifted to vent the brake pipe further until its pressure has been reduced to 20 pounds lower than its normal running pressure. In short, the autoinatio mechanism makes no further reduction in brake pipe pressure it the engineer has manually made a big enough reduction, but adds to whatever reduction the engineer has made until a suflicicnt reduction has been made to correspond with the existing speed.

It should be understood that the particular construction and arrangelnent of parts shown and described is merely illustrative of the invention and thatthcse parts may be considerably modified Without departing from the invention. I desire to have it understood, therefore, that the invention is not limited to the specific disclosure except as indicated in the appended claims.

hat I claim is 1. Automatic means for venting the brake pipe of the usual air-brake system to a predetermined pressure to produce an auto matic b 'ake application comprising, an equalizing reservoir, and automatic means connecting said reservoir to the brake pipe while the engineers valve is in the release, running or.holding positionsand for breaking such connection While the engineers valve is in the lap, service or emergency positions.

In an automatic brake applying mechanism of the character described, the combination with the pipe of the usual air-brake system running from the engineers brake valve to the excess-pressure governor top, automatic means for venting the brake pipe pressure to a predetermined value and including a reservoir, and means effective only while pressure exists in said pipe connected to the excess-pressure governor top for establishing a connection between said reservoir and the brake pipe. i

3. Automatic brakeap lying mechanism of the character describeti comprising au tomatic means for venting the brake pi e to a predetermined pressure, means for (etermining said predetermined pressure to coin form with the actual speed of the vehicle at the time, and means for rendering said pre determined pressure independent of any reduction in brake pipe pressure that may have been made by a manual operation of the engineers brake valve prior to the operation of the automatic venting means.

4. In an automatic brake applying mechanism of the character described, the combination with automatic brake pipe venting means, of a valve controlling [the connection between the brake "pipe and said means, said valve being closed by a. s ring and opened only if the engineers hrafie valve is in the release, running or holding positions.

5. In an automatic brakeapplying mechanism for air-brake systems, the combination with brake pipe venting means including a reservoir and adapted to produce a limited reduction in brake pipe pressure corresponding to a predetermined proportion of the pressure in said reservoir, of means normally ,-onnecting said reservoir to the brake pipe and operable upon movement of the engineers brake valve to a brake applying position to disconnect said reservoir from the brake pipe.

6. In an automatic brake applying mechanism of the character described, means for maintaining a reservoir charged at normal brake pipe pr sure irrespective of any reduction ol pit sure made by manual opera tion of the engineers brake valve comprising, a valve biased to the closed position and opened by pressure, and means including ports and cavities oi the engiueers brake valve for supplying pr *ure to said valve when the engineers valve is in the release, running or holding positions and for exhausting such pressure when said ermineefs valve :is-in the lap or a brake apply ug position.

7. Automatic brake applying apparatus for venting the brake pipe of the usual air brake system to a predetermined yn-essure to produce an automatic brake application of a predetermined extent con'i n'ising, a reservoir, automatic means connecting said reservoir to the brake pipe of the air brake system to charge said reservoir while the engineers brake valve is in the release, running or holding position and for disconnecting said reservoir from the brake pipe while the engineers brake valve is in the lap service or emergency position, and means for venting the brake pipe to an extent depending on the pressure to which said reservoir was charged.

8. Automatic brake applying apparatus for venting the brake pipe of the usual air brake system to a predetermined p1. are to produce an automatic brake application of a pro determined extent comprising, a reservoir, automatic means for connecting said reservoir to the brake pipe while the engineers brake valve is in the release, running or holding position and for disconnecting said reservoir from the brake pipe and trapping the pressure existing in s i l reservoir while the engineers brake valve 1s in the lap position, and automatic means for venting the brake pipe to an extent depending on the pressure trapped in said reservoir.

9. Automatic brake a iplying apparatus for venting the brake pipe of the usual air brake system to a predetermined pressure to produce an automatic brake application of a predetermined extent comprising, a reservoir, the usual brake pipe, a valve controlling the communication of fluid pi ssure between said brake pipe and said reservoir, and automatic means for opening. said valve while the en gineers brake valve is in the release, running or holding posit-ion and for closing said valve while the engineers brake valve is in the lap position.

10. Brake applying apparatus for automatic train control systems superimposed on the usual automatic air brake system in which system a reduction in brake pipe pressure oftects a brake application comprising, a reservoir normally connected to the brake pipe and charged to IIOIHltIl brake pipe pressure, and means for isolating said reservoir from the brake pipe when the usual engineers brake valve is either in the lap or a brake applying position.

11. Brake applying apparatus for auto matic train control systems superimposed on the usual automatic air brake system in which system a reduction in brake pipe pressure ettects a brake application comprising, a reservoir normally connected to the brake pipe and charged to normal brake pipe pressure when the engineers brake valve is in the running position, and means for isolating said reservoir from the brake pipe and trapping brake pipe pressure therein when the usual engineers brake valve moved to a b 'ake applying position, said means functioning i1," respective of whether or not such movement ol. the engineers brake valve actually effects a reduction in brake pipe pressure.

12. Brake control apparatus for air brake system of the type in which the brake pipe is normally charged and in which venting of the brake pipe effects a brake application, an engincers brake val ve for controlling the brakes by venting and charging said brake pipe, and automatically operated brake applying mechanism including a pressure reservoir and a reduction reservoir and controlled by suitable train control mechanism for venting said brake pipe, said b 'ake applying mechanism including means whereby the brake pipe is vented to a predetermined pressure below that of the b -al c pipe pressure existing before a brake application was started even though. the brakes were partially manually applied.

13. In automatic apl'iaratus for controlling an air brake system for train control purposes, the combination with the brake pipe and the engineers brake valve of the air brake system, of a reservoir normally connected to the brake pi pc, a valve controlling said connection. between said reservoir and the brake pipe, said valve being biased to a closed position to interrupt such connection, and means for maintaining said valve open with the engincers brake valve in the running position and for permitting said valve to close simultaneously upon movement of the engineers valve to the lap, service or emergency positions and prior to and independently of any change in the brake pipe pressure resulting from such movement of the engineers valve.

let. In an automatic train control system,

ervoir and the brake pipe while the engineers brake valve is in the positions of lap, service, and emergency. 10

In testimony whereof I hereby affix my signature.

CHARLES S. BUSHNELL. 

